Plain-English definitions, reviewed by an independent investor

Market Index

A market index tracks a basket of stocks to represent a slice or the whole market’s performance.

A market index tracks a basket of stocks to represent a slice or the whole market’s performance.

(A weighted average of selected constituents)

Why it matters

It is the scoreboard everyone quotes and the benchmark most funds try to beat.

Common confusion

An index is unbuyable directly; you track it via funds that replicate it.

Definitions reviewed by the Investing Glossary editorial team.

Frequently Asked Questions

Price-weighted vs cap-weighted?

Some weight by price, most by size; the method changes who leads.

Why index funds?

They aim to match the index cheaply instead of beating it.

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